It is aimed at generating new insights into stem cell physiology and increasing donor availability and safety by achieving engraftment in the absence of graft vs. host disease (GVHD) with dog leukocyte antigen (DLA) haploidentical and matched donor cells. The second area is aimed at understanding the mechanisms whereby growth factors can modify the effects of total body irradiation on production of granulocytes and plateletes. The specific aims are: (1) define the phenotypes of canine hematopoietic progenitors present in the peripheral blood mobilized with growth factors and assay their in vitro and in vivo functions; 2) establish successful stem cell grafts without GVHD in canine litermates which are genotopically DLA-identical or are DLA-haploidentical with the cell donor; and 3) identify which growth factors or combinations are most effective I modifying marrow toxicity of total body irradiation and define the mechanisms responsible for this activity.